The principle of the conductor optical amplifier is similar to that of the rare earth doped fiber amplifier, but there are some differences. The amplification characteristics of the conductor optical amplifier mainly depend on the characteristics of the active layer and the laser cavity. Although it is also a particle number inversion amplification luminescence, the medium of luminescence is non-equilibrium carriers, i.e. electron hole pairs, rather than rare elements. The luminescence of semiconductor can be divided into photoluminescence, electroluminescence and cathodoluminescence according to different excitation modes.